Ferguson has allowed the likes of Phil Neville and Nicky Butt to leave the club in recent years as they fell down the pecking order at Old Trafford, and he was spared a decision on Gary Neville's future when the defender announced his retirement in February.

"It's a horrible thing to say, but you can't be sentimental in this job," Ferguson said in an interview with LMA's The Manager. "I love the players that I've had and I've been very, very fortunate to have had great players who have come through my career with me.

"At Aberdeen there were the likes of Miller, McLeish, and Kennedy, who were a bunch of players that were very loyal to me. At United I've had Giggs, the Nevilles, Scholes and Butt, who represent the spirit of the club.

"All of the players that I have had here have played a part in my success, so when I see something happening, as in the cases of Nicky Butt and Phil Neville, I've had to release them to other opportunities.

"It was getting to the stage that I was terrified of talking to them and telling them they weren't playing. It wasn't fair to them because they were good players and played a big part in the resurrection of Manchester United.

"When the time came for me to let them go, I knew I was cutting really important, loyal strings and I didn't enjoy it."

He added: "My job is to manage United, to produce results and I am no different from any other manager. I'll not be regarded in the same way if I'm not successful.

"Everything to do with me is black and white. If it's on the football field and I see something that I feel is a retrograde step for the club, I have to act and make decisions, which is something that I have always been good at.

"I can make quick decisions and I am lucky that way. In management, you have to be able to make decisions - sometimes you're not right, but that doesn't concern me too much because the important thing is being able to do it."

Ferguson has been given the stability to make firm decisions without fear of the sack having won 46 trophies in 37 years of management, but there was talk he would be dismissed before he delivered the FA Cup to United in 1990.

That was his first trophy after four years at the club, and he feels that made a huge difference to his standing at Old Trafford.

"I would never have expected to achieve what I have achieved," he said. "There have been periods where there have been sudden leaps. Going to Aberdeen took me to a different level and it was an opportunity I grasped.

"When we won our first trophy at Manchester United there was that sudden leap of confidence and a sense that I was safe in the job.

"That stability is important, not for me, but for the players, because when they know who the manager is going to be every day it makes an immense difference to the structure, the confidence and the power base of the club, there's no doubt about that."